One of the very first steps when it comes to diagnosing your home air conditioner, refrigerator, or even your vehicle’s air conditioner is understanding the temperature and the current pressure that your system is operating at. Having these facts along with the saturation point, the subcool, and the superheat numbers for the refrigerant you are working on are essential when it comes to really understanding what is going wrong with your system.
After a visual inspection the very next step for the most seasoned technicians is pulling out their gauges and checking the pressure and temperature. It just becomes second nature after enough calls. I have heard stories of rookie techs calling some of the pros on their team for help on a system that they’re stuck on. It doesn’t matter what the situation is. It doesn’t matter if you’re in Miami or in Fargo. It will never fail that one of the first questions the pros ask the rookie is what is your subcool and what is your superheat? Having and understanding these numbers is key to figuring out what to do next.
But, these numbers won’t do you any good if you don’t know what refrigerant you are dealing with and what the refrigerant’s boiling point is at each pressure level. This article aims at providing you with just that information.
R-448A Solstice N40 Basic Info
It seems that as the years go by we face more and more pressure to begin phasing down HFC refrigerants. As I write this article most HFCs have already been phased down across the European Union and we are not too far behind here in the United States. When a class of refrigerants are phased out there obviously needs to be another to step up and take their place. The debate is still raging on rather that should be natural refrigerants or if we should go with the newer class of refrigerants known as Hydrofluoroolefins (HFOs).
The newer refrigerant R-448A, also known as Solstice N40, is an HFO refrigerant. It was introduced by the Honeywell corporation under their new Solstice brand line. While 448A can technically be classified as an HFO refrigerant it actually has more HFC refrigerants in it. This refrigerant is a zeotropic blend of R-32 (26%), R-125 (26%), R-134a (21%), R-1234ze (7%), and R-1234yf (20%). This N40 refrigerant was designed to replace the ever popular HCFC R-22 and the HFC R-404A.
It can be used for new installations and in retrofits. I won’t get into retrofitting here, but there are many guides from OEMs and Honeywell that take you through step by step. One word of warning though is if you are trying to retrofit an R-22 unit over to this refrigerant you should know that R-448A requires POE oil while R-22 requires mineral oil. They are not interchangeable. R-404A does use POE oil so there won’t be a problem there.
This refrigerant is designed for use in low and medium temperature applications such as supermarket refrigeration, refrigerated cold stores, refrigerated transport vending machines, and industrial refrigeration. This N40 refrigerant from Honeywell has an A1 safety rating from ASHRAE. What that means is that the refrigerant is non-toxic and is not flammable. That is a big deal as so many refrigerants nowadays are rated either flammable or slightly flammable.
As I had mentioned earlier, the main point of switching to these new HFO refrigerants is to protect the climate. In the case of R-448A you will see a sixty-eight percent reduction in Global Warming Potential (GWP). That is a significant reduction. Let’s look at the numbers. R-404A has a total GWP of nearly four-thousand. R-448A has a GWP of fourteen-hundred. Along with the savings of GWP you will also find that this Solstice refrigerant runs between five to ten percent more efficient then R-404A. SO, you’ll get the benefit to the climate in two ways.
There is one big downside here on this refrigerant I want to mention before I get to the PT chart. I had stated that the GWP for this product is fourteen-hundred. While it is lower then R-404A you should be aware that it is still a very high GWP number. Because this number is so high I do not foresee this refrigerant lasting in the long run. Its GWP is just too high. I would fully predict that we would see this refrigerant being phased out in just about five years time. It will be replaced by something else down the road. This refrigerant is just a stop gap until we find something better.
Alright folks, I’ve talked enough. Let’s get to the pressure temperature chart. As you are looking over this data please reach out to me if you find something that is not correct. I strive to make these tables accurate and will get any errors corrected as soon as I can.
R-448A Solstice N40 PT Chart
| PSIG | Liquid Temp (F) | Liquid Temp (C) | Vapor Temp (F) | Vapor Temp (C) |
|---|---|---|---|---|
| 0 | -51 | -46.11 | -39.9 | -39.94 |
| 1 | -48.6 | -44.78 | -37.5 | -38.61 |
| 2 | -46.2 | -43.44 | -35.2 | -37.33 |
| 3 | -44 | -42.22 | -32.9 | -36.06 |
| 4 | -41.9 | -41.06 | -30.8 | -34.89 |
| 5 | -39.8 | -39.89 | -28.8 | -33.78 |
| 6 | -37.8 | -38.78 | -26.9 | -32.72 |
| 7 | -35.9 | -37.72 | -25 | -31.67 |
| 8 | -34.1 | -36.72 | -23.2 | -30.67 |
| 9 | -32.4 | -35.78 | -21.4 | -29.67 |
| 10 | -30.6 | -34.78 | -19.7 | -28.72 |
| 11 | -29 | -33.89 | -18.1 | -27.83 |
| 12 | -27.4 | -33 | -16.5 | -26.94 |
| 13 | -25.8 | -32.11 | -15 | -26.11 |
| 14 | -24.3 | -31.28 | -13.5 | -25.28 |
| 16 | -21.4 | -29.67 | -10.6 | -23.67 |
| 18 | -18.6 | -28.11 | -7.8 | -22.11 |
| 20 | -16 | -26.67 | -5.2 | -20.67 |
| 22 | -13.5 | -25.28 | -2.7 | -19.28 |
| 24 | -11 | -23.89 | -0.3 | -17.94 |
| 26 | -8.7 | -22.61 | 2 | -16.67 |
| 28 | -6.5 | -21.39 | 4.2 | -15.44 |
| 29 | -5.4 | -20.78 | 5.3 | -14.83 |
| 31 | -3.3 | -19.61 | 7.4 | -13.67 |
| 34 | -0.2 | -17.89 | 10.4 | -12 |
| 37 | 2.7 | -16.28 | 13.3 | -10.39 |
| 40 | 5.5 | -14.72 | 16 | -8.89 |
| 43 | 8.2 | -13.22 | 18.7 | -7.39 |
| 46 | 10.8 | -11.78 | 21.2 | -6 |
| 49 | 13.2 | -10.44 | 23.7 | -4.61 |
| 52 | 15.6 | -9.11 | 26 | -3.33 |
| 55 | 17.9 | -7.83 | 28.3 | -2.06 |
| 59 | 20.9 | -6.17 | 31.2 | -0.44 |
| 63 | 23.8 | -4.56 | 34 | 1.11 |
| 67 | 26.5 | -3.06 | 36.7 | 2.61 |
| 83 | 36.5 | 2.5 | 46.6 | 8.11 |
| 101 | 46.5 | 8.06 | 56.3 | 13.5 |
| 121 | 56.2 | 13.44 | 65.9 | 18.83 |
| 142 | 65.4 | 18.56 | 74.9 | 23.83 |
| 154 | 70.2 | 21.22 | 79.6 | 26.44 |
| 167 | 75.1 | 23.94 | 84.4 | 29.11 |
| 181 | 80.2 | 26.78 | 89.3 | 31.83 |
| 196 | 85.3 | 29.61 | 94.3 | 34.61 |
| 212 | 90.5 | 32.5 | 99.3 | 37.39 |
| 229 | 95.7 | 35.39 | 104.3 | 40.17 |
| 246 | 100.7 | 38.17 | 109.1 | 42.83 |
| 264 | 105.6 | 40.89 | 113.9 | 45.5 |
| 284 | 110.9 | 43.83 | 119 | 48.33 |
| 304 | 115.9 | 46.61 | 123.8 | 51 |
| 325 | 121 | 49.44 | 128.6 | 53.67 |
| 348 | 126.2 | 52.33 | 133.6 | 56.44 |
| 349 | 126.4 | 52.44 | 133.8 | 56.56 |
| 372 | 131.4 | 55.22 | 138.5 | 59.17 |
| 397 | 136.6 | 58.11 | 143.4 | 61.89 |
| 423 | 141.8 | 61 | 148.3 | 64.61 |
| 450 | 146.9 | 63.83 | 153 | 67.22 |